This touches on what I consider to be a universal truth about human interaction. If you have a hidden agenda / ulterior motive (like getting a phone number in y

This touches on what I consider to be a universal truth about human interaction. If you have a hidden agenda / ulterior motive (like getting a phone number in your example), other people will usually sense it as it comes across in body language and demeanour, and not just via speaking. People have a natural negative reaction to shiftiness. If however you aren't looking to gain anything w/ the interaction other than enjoying the interaction itself, you will get a positive response nearly every time. Sometimes people might be unresponsive due to a bad mood or general unhappiness, but who cares? You had no agenda, so you have nothing invested. If you let it roll off and move along you literally lose nothing.